Apparatus and method for tracking synchronization in wireless communication system

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). A terminal and method of the terminal in a wireless communication system are provided. The terminal includes at least one transceiver and at least one processor operatively connected to the at least one transceiver. The at least one processor is configured to acquire synchronization information of a first beam which is a serving beam, update the synchronization information based on the first beam or at least one second beam, determine at least one channel quality of the at least one second beam based on the updated synchronization information, and update the serving beam based on the at least one channel quality.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/295,602, filed on Mar. 7, 2019, which will be issued as U.S. Pat.No. 11,259,257 on Feb. 22, 2022, which is based on and claimed priorityunder 35 U.S.C. § 119(a) of a Korean patent application number10-2018-0027090, filed on Mar. 7, 2018, in the Korean IntellectualProperty Office, the disclosure of which is incorporated by referenceherein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a wireless communication system. Moreparticularly, the disclosure relates to terminal and a method fortracking synchronization in a wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4^(th) generation (4G) communication systems, efforts havebeen made to develop an improved 5^(th) generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post long term evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as toaccomplish higher data rates. To decrease propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesare discussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

In order to overcome the path loss problem caused by the characteristicsof an ultra-high frequency (mmWave) band, a 5G communication system isoperated to increase signal gain by using a beamforming technique. In abeamforming-based wireless communication system, a terminal not onlyperforms synchronization tracking in order to manage the acquiredsynchronization, but also performs beam tracking in order to controlmobility or a channel change. Synchronization tracking uses a servingbeam and beam tracking uses other beams as well as a serving beam, andthus, when interworking between synchronization tracking and beamtracking is not considered, a synchronization failure (orout-of-synchronization) may occur or beam tracking according to mobilitymay not be performed smoothly.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea terminal and a method for effectively tracking beamforming-basedsynchronization in a wireless communication system.

Another aspect of the disclosure is to provide a terminal and a methodfor tracking a beam by considering synchronization in a wirelesscommunication system.

Another aspect of the disclosure is to provide a terminal and a methodfor efficiently performing interworking between synchronization trackingand beam tracking in a wireless communication system.

Another aspect of the disclosure is to provide a terminal and a methodfor performing synchronization tracking by using any beam in a wirelesscommunication system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a terminal in a wirelesscommunication system is provided. The terminal includes at least onetransceiver and at least one processor operatively connected to the atleast one transceiver. The at least one processor is configured toacquire synchronization information of a first beam which is a servingbeam, update the synchronization information based on the first beam orat least one second beam, determine at least one channel quality of theat least one second beam based on the updated synchronizationinformation, and update the serving beam based on the at least onechannel quality.

In accordance with another aspect of the disclosure, a method of aterminal in a wireless communication system is provided. The methodincludes acquiring synchronization information of a first beam which isa serving beam, updating the synchronization information based on thefirst beam or at least one second beam, determining at least one channelquality of the at least one second beam based on the updatedsynchronization information, and updating the serving beam based on theat least one channel quality.

A terminal and a method according to various embodiments perform beamtracking by considering synchronization tracking, and thus canefficiently manage synchronization and mobility in a beamforming system.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a configuration of a wireless communication systemaccording to various embodiments of the disclosure;

FIG. 2 is a block diagram illustrating an example of a configuration ofa base station in a wireless communication system according to variousembodiments of the disclosure;

FIG. 3 is a block diagram illustrating an example of a configuration ofa terminal in a wireless communication system according to variousembodiments of the disclosure;

FIG. 4A is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure;

FIG. 4B is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure;

FIG. 4C is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure;

FIG. 5 illustrates an example of synchronization tracking and beamtracking according to various embodiments of the disclosure;

FIG. 6 is a flowchart illustrating an operation of a terminal forinterworking between synchronization tracking and beam trackingaccording to various embodiments of the disclosure;

FIG. 7 is a flowchart illustrating an operation of a terminal for fixedinterworking between serving-beam-based synchronization tracking andbeam tracking according to various embodiments of the disclosure;

FIG. 8 is a flowchart illustrating an operation of a terminal foradaptive interworking between serving-beam-based synchronizationtracking and beam tracking according to various embodiments of thedisclosure;

FIG. 9 illustrates an example of fixed interworking betweenserving-beam-based synchronization tracking and beam tracking accordingto various embodiments of the disclosure;

FIG. 10 is a flowchart illustrating an operation of a terminal forinterworking between any-beam-based synchronization tracking and beamtracking according to various embodiments of the disclosure;

FIG. 11 is a flowchart illustrating an operation of a terminal forbeam-based synchronization tracking according to various embodiments ofthe disclosure;

FIG. 12 illustrates an example of interference during any-beam-basedsynchronization tracking according to various embodiments of thedisclosure;

FIG. 13A illustrates an example of filtering out interference duringany-beam-based synchronization tracking according to various embodimentsof the disclosure;

FIG. 13B illustrates another example of filtering out interferenceduring any-beam-based synchronization tracking according to variousembodiments of the disclosure;

FIG. 13C illustrates still another example of filtering out interferenceduring any-beam-based synchronization tracking according to variousembodiments of the disclosure;

FIG. 14 is a flowchart illustrating an operation of a terminal foron-demand interworking between serving-beam-based synchronizationtracking and beam tracking according to various embodiments of thedisclosure;

FIG. 15A is a flowchart illustrating an operation of a terminal fordetermining whether to perform serving-beam-based synchronizationtracking according to various embodiments of the disclosure;

FIG. 15B is a flowchart illustrating another operation of a terminal fordetermining whether to perform serving-beam-based synchronizationtracking according to various embodiments of the disclosure;

FIG. 15C is a flowchart illustrating still another operation of aterminal for determining whether to perform serving-beam-basedsynchronization tracking according to various embodiments of thedisclosure;

FIG. 16 is a flowchart illustrating an operation of a terminal forupdating a serving beam according to various embodiments of thedisclosure; and

FIG. 17 is a block diagram illustrating an example of managingsynchronization information according to various embodiments of thedisclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

All terms used herein, including technical terms and scientific terms,have the same meanings as commonly understood by those having commonknowledge in the technical field to which the disclosure pertains. Suchterms as those defined in a generally-used dictionary among the terms asused in the disclosure are to be interpreted to have the meaningsidentical or similar to the contextual meanings in the relevant field ofart, and are not to be interpreted to have ideal or excessively formalmeanings unless clearly defined in the disclosure. In some cases, eventhe term defined in the disclosure should not be interpreted to excludeembodiments.

In various embodiments as described hereinafter, a hardware-basedapproach will be described as an example. However, various embodimentsinclude technology that uses both hardware and software and thus do notexclude a software-based approach.

The disclosure described below relates to a terminal and a method for,in a wireless communication system, interworking between:synchronization tracking for management of synchronization so as toprevent out-of-synchronization; and beam tracking for search for anoptimal beam. Specifically, in the disclosure, a description will bemade of technology for, in a wireless communication system, controllinga time point, a condition, a situation, and the like, at/in which eachof synchronization tracking and beam tracking is performed, therebycontrolling a terminal to prevent the occurrence ofout-of-synchronization and searching for an optimal beam according tomobility of a terminal or a change of a wireless channel.

The terms in the following description are used for convenience ofdescription and illustrative purposes to refer to: synchronizationacquisition (e.g., synchronization success and out-of-synchronization);signals (e.g., channel and block); beams (e.g., serving beam andneighboring beam); network entities (e.g., base station and cell);elements of a terminal; and the like. Accordingly, the disclosure is notlimited to the following terms and other terms having equivalenttechnical meanings may be used.

Also, in the disclosure, various embodiments are described using theterms used in some communication standards (e.g., 3rd generationpartnership project (3GPP)), but this configuration is only an examplefor description. Various embodiments may also be easily modified andapplied to another communication system.

FIG. 1 illustrates a configuration of a wireless communication systemaccording to various embodiments of the disclosure.

FIG. 1 illustrates an example of a base station 110, a terminal 120, anda terminal 130 as some of nodes using a wireless channel in a wirelesscommunication system.

The base station 110 and the terminals 120 and 130 are a networkinfrastructure which provides radio access. The base station 110 has acoverage defined by a predetermined geographic area based on thedistance over which a signal can be transmitted. The base station 110may be referred to as an “access point (AP),” an “eNodeB (eNB),” a “5thgeneration node (5G node),” a “wireless point,” or other terms having anequivalent technical meaning According to various embodiments, the basestation 110 may be connected to at least one transmission/receptionpoint (TRP). Through at least one TRP, the base station 110 may transmita downlink (DL) signal to the terminal 120 or 130, or may receive anuplink (UL) signal therefrom.

Each of the terminals 120 and 130 is a terminal used by a user, andperforms communication with the base station 110 through a wirelesschannel. In some cases, at least one of the terminals 120 and 130 may beoperated without user involvement. That is, at least one of theterminals 120 and 130 is a terminal that performs machine-typecommunication (MTC), and may not be carried by a user. Each of theterminals 120 and 130 may be referred to as a “user equipment (UE),” a“mobile station,” a “subscriber station,” a “customer premises equipment(CPE),” a “remote terminal,” a “wireless terminal,” an “electronicdevice,” a “user device,” or other terms having an equivalent technicalmeaning.

The base station 110 and the terminals 120 and 130 may transmit andreceive radio signals in a millimeter wave (mmWave) band (e.g., 28 GHz,30 GHz, 38 GHz, or 60 GHz). In this example, in order to improve achannel gain, the base station 110 and the terminals 120 and 130 mayperform beamforming. In this example, the beamforming may includetransmission beamforming and reception beamforming That is, the basestation 110 and the terminals 120 and 130 may assign directivity to atransmission signal or a reception signal. To this end, the base station110 and the terminals 120 and 130 may select serving beams 112, 113,121, and 131 through a beam search procedure or a beam managementprocedure. After the serving beams 112, 113, 121, and 131 are selected,subsequent communication may be performed through a resource in aquasi-co-located (QCL) relationship with a resource for transmission ofthe serving beams 112, 113, 121, and 131.

When large-scale properties of a channel, through which a symbol on afirst antenna port has been delivered, can be inferred from a channelthrough which a symbol on a second antenna port has been delivered, thefirst and second antenna ports may be regarded as having a QCLrelationship. For example, the large-scale properties may include atleast one of a delay spread, a Doppler spread, a Doppler shift, anaverage gain, an average delay, and a spatial receiver parameter.

The terminal 120 may receive a signal from the base station 110 by usinga beam, or may transmit a signal to the base station 110 by using abeam. In order to transmit or receive a signal to or from the basestation 110, the terminal 120 may acquire synchronization and may managesynchronization so that the acquired synchronization is within anallowable range (hereinafter “synchronization range”). In order totransmit a signal to the base station 110 or receive a signal therefromin a smooth channel environment, the terminal 120 may determine channelqualities of beams, and may identify an optimal beam based on thedetermined channel qualities.

In order to manage synchronization, the terminal 120 may schedule theserving beam used when synchronization is acquired. In order to identifyan optimal beam, the terminal 120 may schedule neighboring beams as wellas a serving beam. Hereinafter, in the disclosure, a description will bemade of a method for effectively scheduling a beam in order to managesynchronization and identify an optimal beam, that is, a method forinterworking between synchronization tracking and beam tracking.

FIG. 2 is a block diagram illustrating an example of a configuration ofa base station in a wireless communication system according to variousembodiments of the disclosure.

The configuration illustrated in FIG. 2 may be understood as aconfiguration of the base station 110. The term “ . . . unit,” the termending with the suffix “ . . . or” or “ . . . er,” or the like, which isused below, may signify a unit of processing at least one function oroperation, and this configuration may be implemented in hardware,software, or as a combination of hardware and software.

Referring to FIG. 2 , the base station 110 may include a wirelesscommunication unit 210, a backhaul communication unit 220, a storageunit 230, and a controller 240.

The wireless communication unit 210 is configured to perform functionsfor transmitting or receiving a signal through a wireless channel. Forexample, the wireless communication unit 210 is configured to perform afunction of conversion between a baseband signal and a bit streamaccording to a physical layer standard of the system. For example, thewireless communication unit 210 is configured to, when data istransmitted, generate complex symbols by encoding and modulating atransmission bit stream. Also, the wireless communication unit 210 isconfigured to, when data is received, restore a reception bit stream bydemodulating and decoding a baseband signal. Further, the wirelesscommunication unit 210 is configured to up-convert a baseband signalinto a radio frequency (RF) band signal and then transmit the RF bandsignal through an antenna, and is configured to down-convert an RF bandsignal received through the antenna into a baseband signal.

To this end, the wireless communication unit 210 may include atransmission filter, a reception filter, an amplifier, a mixer, anoscillator, a digital-to-analog converter (DAC), an analog-to-digitalconverter (ADC), and the like. Also, the wireless communication unit 210may include multiple transmission/reception paths. Further, the wirelesscommunication unit 210 may include at least one antenna array includingmultiple antenna elements. In terms of hardware, the wirelesscommunication unit 210 may include a digital unit and an analog unit,and the analog unit may include multiple sub-units according tooperating power, an operating frequency, and the like.

The wireless communication unit 210 may transmit or receive a signal.For example, the wireless communication unit 210 may transmit asynchronization signal (SS), a reference signal (RS), systeminformation, a message, control information, data, or the like. Also,the wireless communication unit 210 may perform beamforming Further, inorder to assign directivity, which depends on a configuration by thecontroller 240, to a signal to be transmitted or received, the wirelesscommunication unit 210 may apply a beamforming weight to the signal. Thewireless communication unit 210 may repeatedly transmit a signal bychanging a beam being formed.

As described above, the wireless communication unit 210 transmits andreceives signals. Accordingly, the entirety or part of the wirelesscommunication unit 210 may be referred to as a “transmitter,” a“receiver,” or a “transceiver.” Also, in the following description,transmission and reception performed through a wireless channel has ameaning including the execution of the above-described processing by thewireless communication unit 210.

The backhaul communication unit 220 is configured to provide aninterface configured to perform communication with other nodes within anetwork. That is, the backhaul communication unit 220 is configured toconvert a bit stream transmitted from the base station 110 to anothernode, for example, another access node, another base station, a highernode, a core network, and the like, into a physical signal, and isconfigured to convert a physical signal received from another node intoa bit stream.

The storage unit 230 is configured to store data, such as a basicprogram for operation of the base station 110, an application program,and configuration information. The storage unit 230 may be implementedby a volatile memory, a non-volatile memory, or a combination of avolatile memory and a non-volatile memory. Also, the storage unit 230 isconfigured to provide stored data in response to a request of thecontroller 240.

The controller 240 is configured to control an overall operation of thebase station 110. For example, the controller 240 is configured totransmit and receive signals through the wireless communication unit 210or through the backhaul communication unit 220. Also, the controller 240is configured to record data in the storage unit 230 and read therecorded data therefrom. Further, the controller 240 may be configuredto perform functions of a protocol stack required by the communicationstandard. To this end, the controller 240 may include at least oneprocessor. According to various embodiments, the controller 240 may beconfigured to control the base station 110 to perform operationsaccording to various embodiments described below.

FIG. 3 is a block diagram illustrating an example of a configuration ofa terminal in a wireless communication system according to variousembodiments of the disclosure.

The configuration illustrated in FIG. 3 may be understood as aconfiguration of the terminal 120. The term “ . . . unit,” the termending with the suffix “ . . . or” or “ . . . er,” or the like, which isused below, may signify a unit of processing at least one function oroperation, and this configuration may be implemented in hardware,software, or as a combination of hardware and software.

Referring to FIG. 3 , the terminal 120 includes a communication unit310, a storage unit 320, and a controller 330.

The communication unit 310 is configured to perform functions fortransmitting or receiving a signal through a wireless channel. Forexample, the communication unit 310 is configured to perform a functionof conversion between a baseband signal and a bit stream according to aphysical layer standard of the system. For example, the communicationunit 310 is configured to, when data is transmitted, generate complexsymbols by encoding and modulating a transmission bit stream. Also, thecommunication unit 310 is configured to, when data is received, restorea reception bit stream by demodulating and decoding a baseband signal.Further, the communication unit 310 is configured to up-convert abaseband signal into an RF band signal and then transmit the RF bandsignal through an antenna, and is configured to down-convert an RF bandsignal received through the antenna into a baseband signal. For example,the communication unit 310 may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,and the like.

Also, the communication unit 310 may include multipletransmission/reception paths. Further, the communication unit 310 mayinclude at least one antenna array including multiple antenna elements.In terms of hardware, the communication unit 310 may include a digitalcircuitry and an analog circuitry (e.g., a radio frequency integratedcircuit (RFIC)). In this example, the digital circuitry and the analogcircuitry may be implemented as one package. Also, the communicationunit 310 may include multiple RF chains. The communication unit 310 mayperform beamforming. Further, in order to assign directivity, whichdepends on a configuration by the controller 330, to a signal to betransmitted or received, the communication unit 310 may apply abeamforming weight to the signal. According to an embodiment, thecommunication unit 310 may include an RF block. The RF block may includea first RF circuitry related to an antenna and a second RF circuitryrelated to baseband processing. The first RF circuitry may be referredto as an “RF-antenna (A).” The second RF circuitry may be referred to asan “RF-baseband(B).”

Also, the communication unit 310 may transmit or receive a signal. Thecommunication unit 310 may receive a DL signal. A DL signal may includea synchronization signal, a reference signal, system information, aconfiguration message, control information, DL data, or the like. Also,the communication unit 310 may transmit an UL signal. An UL signal mayinclude a random access-related signal, a reference signal (e.g., asounding reference signal (SRS) or a demodulation RS (DM-RS)), UL data,or the like. Also, the communication unit 310 may include differentcommunication modules configured to process signals in differentfrequency bands. Further, the communication unit 310 may includemultiple communication modules configured to support multiple differentradio access technologies. For example, different radio accesstechnologies may include Bluetooth low energy (BLE), Wi-Fi, Wi-FiGigabyte (WiGig), a cellular network (e.g., a long-term evolution (LTE)network or a new radio (NR) network), and the like. Also, differentfrequency bands may include a super-high frequency (SHF) (e.g., 2.5 GHzor 5 GHz) band, a mmWave (e.g., 38 GHz or 60 GHz) band, and the like.

As described above, the communication unit 310 transmits and receivessignals. Accordingly, the entirety or part of the communication unit 310may be referred to as a “transmitter,” a “receiver,” or a “transceiver.”Also, in the following description, transmission and reception performedthrough a wireless channel has a meaning including the execution of theabove-described processing by the communication unit 310.

The storage unit 320 is configured to store data, such as a basicprogram for operation of the terminal 120, an application program, andconfiguration information. The storage unit 320 may be implemented by avolatile memory, a non-volatile memory, or a combination of a volatilememory and a non-volatile memory. Also, the storage unit 320 isconfigured to provide stored data in response to a request of thecontroller 330. According to various embodiments, the storage unit 320may be configured to store beam information. Beam information mayinclude information for identification of a beam of the terminal.According to various embodiments, the storage unit 320 may be configuredto store beam-specific channel information. For example, the terminalmay be configured to, when a signal is received using a beam of theterminal, store a measurement result of the signal. Also, according tovarious embodiments, the storage unit 320 may be configured to storesynchronization-related information of each of beams of the terminal.

The controller 330 is configured to control an overall operation of theterminal 120. For example, the controller 330 is configured to transmitand receive signals through the communication unit 310. Also, thecontroller 330 is configured to record data in the storage unit 320 andread the recorded data therefrom. Further, the controller 330 may beconfigured to perform functions of a protocol stack required by thecommunication standard. To this end, the controller 330 may include atleast one processor or a microprocessor, or may be part of a processor.In addition, the controller 330 and a part of the communication unit 310may be referred to as a “communication processor (CP).” The controller330 may include various modules configured to perform communication.

According to various embodiments, the controller 330 may include asynchronization tracker 331 and a beam tracker 333. The synchronizationtracker 331 may be configured to acquire synchronization and managesynchronization by correcting an error having occurred. According tosome embodiments, the synchronization tracker 331 may further include amonitoring unit configured to check an error which occurs whensynchronization is acquired for each beam and a filter configured tocontrol interference to with a neighboring cell. The beam tracker 333may be configured to change beams so as to measure channel qualities ofthe respective beams, and determine an optimal beam based on the channelqualities. In this example, each of the synchronization tracker 331 andthe beam tracker 333 is an instruction set or codes stored in thestorage unit 320, and may be instructions/codes or a storage spacestoring the instructions/codes, which are, at least temporarily, residedin the controller 330, or may be a part of a circuitry constituting thecontroller 330 or a module configured to perform functions of thecontroller 330. According to various embodiments, the controller 330 maybe configured to control the terminal to perform operations according tovarious embodiments described below.

The configuration of the terminal illustrated in FIG. 3 is only anexample of a terminal, and thus the disclosure is not limited thereto.That is, according to various embodiments, some elements of the terminalmay be added, deleted, or modified.

FIG. 4A is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure.

FIG. 4B is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure.

FIG. 4C is a block diagram illustrating a configuration of acommunication unit in a wireless communication system according tovarious embodiments of the disclosure.

FIG. 4A illustrates an example of a specific configuration of thewireless communication unit 210 of FIG. 2 or the communication unit 310of FIG. 3 .

FIG. 4B illustrates an example of a specific configuration of thewireless communication unit 210 of FIG. 2 or the communication unit 310of FIG. 3 .

FIG. 4C illustrates an example of a specific configuration of thewireless communication unit 210 of FIG. 2 or the communication unit 310of FIG. 3 .

Specifically, FIG. 4A illustrates a part of the wireless communicationunit 210 of FIG. 2 or the communication unit 310 of FIG. 3 , andillustrates an example of elements configured to perform beamforming.

Specifically, FIG. 4B illustrates a part of the wireless communicationunit 210 of FIG. 2 or the communication unit 310 of FIG. 3 , andillustrates an example of elements configured to perform beamforming.

Specifically, FIG. 4C illustrates a part of the wireless communicationunit 210 of FIG. 2 or the communication unit 310 of FIG. 3 , andillustrates an example of elements configured to perform beamforming.

Referring to FIG. 4A, the wireless communication unit 210 or thecommunication unit 310 may include an encoder/modulator 402, a digitalbeamformer 404, multiple transmission paths 406-1 to 406-N, and ananalog beamformer 408.

The encoder/modulator 402 is configured to perform channel encoding. Forchannel encoding, at least one of a low-density parity-check (LDPC)code, a convolution code, and a polar code may be used. Theencoder/modulator 402 is configured to generate modulated symbols byperforming constellation mapping.

The digital beamformer 404 is configured to perform beamforming on adigital signal (e.g., modulated symbols). To this end, the digitalbeamformer 404 is configured to multiply the modulated symbols bybeamforming weights. In this example, the beamforming weights may beused to change the magnitude or the phase of a signal, and may bereferred to as a “precoding matrix,” “precoder,” or the like. Thedigital beamformer 404 is configured to output digital-beamformedmodulated symbols to the multiple transmission paths 406-1 to 406-N. Inthis example, according to a multiple-input multiple-output (MIMO)transmission technique, the modulated symbols may be multiplexed, oridentical modulated symbols may be provided to the multiple transmissionpaths 406-1 to 406-N.

The multiple transmission paths 406-1 to 406-N are configured to convertthe digital-beamformed digital signals into analog signals. To this end,each of the multiple transmission paths 406-1 to 406-N may include aninverse fast fourier transform (IFFT) calculator, a cyclic prefix (CP)inserter, a DAC, and an up-converter. The CP inserter may be used for anorthogonal frequency division multiplexing (OFDM) method, and may beexcluded when another physical layer method (e.g., a filter bankmulti-carrier (FBMC)) is applied. That is, the multiple transmissionpaths 406-1 to 406-N are configured to provide an independent signalprocessing process with respect to multiple streams generated by digitalbeamforming. However, according to an implementation method, some of theelements of the multiple transmission paths 406-1 to 406-N may beshared.

The analog beamformer 408 is configured to perform beamforming on ananalogue signal. To this end, the digital beamformer 404 is configuredto multiply analog signals by beamforming weights. In this example, thebeamforming weights may be used to change the magnitude and the phase ofa signal. Specifically, according to a connection structure between themultiple transmission paths 406-1 to 406-N and antennas, the analogbeamformer 408 may be configured as illustrated in FIG. 4B or 4C.

Referring to FIG. 4B, signals input to the analog beamformer 408 passthrough phase/magnitude conversion calculation and amplificationcalculation and are then transmitted through the antennas. In thisexample, signals along the respective paths are transmitted throughdifferent antenna sets, that is, antenna arrays. Processing of a signalinput through the first path is described. The signal is converted intoa signal sequence having different or identical phase/magnitude byphase/magnitude converters 412-1-1, 412-1-2, . . . , 412-1-M, the signalsequence is amplified by amplifiers 414-1-1, 414-1-2, . . . , 414-1-M,and then the amplified signal sequence is transmitted through theantennas. A signal through each of the paths 406-1 . . . 406-N would beprocessed similarly, through via phase/magnitude converters 412-1-1,412-1-2, . . . , 412-N-1, 412-N-2, . . . , 412-N-M and amplifiers414-1-1, 414-1-2, . . . , 414-N-1, 414-N-2, . . . , 414-N-M.

Referring to FIG. 4C, signals input to the analog beamformer 408 passthrough phase/magnitude conversion calculation and amplificationcalculation and are then transmitted through the antennas. In thisexample, signals along the respective paths are transmitted through anidentical antenna set, that is, an antenna array. Processing of a signalinput through the first path is described. The signal is converted intoa signal sequence having different or identical phase/magnitude byphase/magnitude converters 412-1-1 to 412-1-M, and the signal sequenceis amplified by amplifiers 414-1-1 to 414-1-M. Then, so that theamplified signals are transmitted through one antenna array, theamplified signals are added by adders 416-1, 416-2, . . . , 416-M withreference to an antenna element, and then the added signals aretransmitted through the antennas.

FIG. 4B illustrates an example of using an independent antenna array foreach transmission path, and FIG. 4C illustrates an example of sharing ofone antenna array by transmission paths. However, according to anotherembodiment, some transmission paths may use independent antenna arraysand the remaining transmission paths may share one antenna array.Further, according to still another embodiment, a switchable structureis applied between transmission paths and antenna arrays, so that it ispossible to use a structure adaptively changeable according to thecircumstances.

In order to communicate with the base station, the terminal is requiredto acquire synchronization. Hereinafter, in the disclosure, acquisitionof synchronization implies that the terminal acquires information on aresource structure (e.g., a boundary between subframes, slots, symbols,resource blocks, or frequencies) with the base station within apredetermined error range. Out-of-synchronization implies that thedifference between the information on the resource structure acquired bythe terminal and information on an actual resource structure of the basestation is outside a predetermined error range. In some embodiments,when the synchronization information is acquired, the terminal isfurther configured to acquire information on a resource structure with abase station within a predetermined error range.

In order not to lose the acquired synchronization, the terminal maycontinuously track synchronization. In a beamforming communicationsystem, due to the directivity of a beam, synchronizations may bedifferent according to beams. The terminal is required to tracksynchronization of the beam of the terminal used when synchronization isacquired.

The terminal may move, tilt, or rotate. Also, in a wireless channelenvironment between the terminal and the base station, a new obstaclemay appear or topography may change. Due to this channel change, anoptimal beam appropriate for execution of communication is not fixed. Inorder to continuously update to a beam appropriate for communication,the terminal is required to continuously measure qualities of beams.

When the terminal schedules beams thereof in order to perform beamtracking, the number of times of scheduling of a serving beam may berelatively reduced. As the number of times of scheduling of a servingbeam is reduced, the opportunity for synchronization tracking using theserving beam may be reduced. When the opportunity for synchronizationtracking using the serving beam is reduced, out-of-synchronization maybe caused. In contrast, when the number of times of scheduling of theserving beam is exceedingly increased, the opportunity for measuringqualities of neighboring beams is relatively reduced, and thus thedegradation of communication quality may be caused.

In order to solve the above-mentioned problems, a terminal according tovarious embodiments performs operations for interworking betweensynchronization tracking and beam tracking. In the disclosure, adescription will be made of a method for combining synchronizationtracking and beam tracking and performing the combined synchronizationtracking and beam tracking and thus enabling a reduction in asynchronization failure rate and smooth identification of an optimalbeam.

For convenience of description, a beam tracking procedure using DLsignals to a terminal from a base station will be described by way ofexample, but the disclosure is not limited thereto. In other words, beamtracking according to the disclosure can be utilized for DL signals, ULsignals, signals for device-to-device (D2D) communication (e.g.,sidelink (SL)), and all other signals using beams.

FIG. 5 illustrates an example of synchronization tracking and beamtracking according to various embodiments of the disclosure.

Hereinafter, in FIG. 5 , terms and configurations required to describesynchronization tracking and beam tracking according to the disclosurewill be defined. However, it goes without saying that the disclosure isnot limited to the terms defined in FIG. 5 and other terms havingequivalent technical meanings may be used. Also, in FIG. 5 , in order todescribe beam tracking, a situation in which a base station and aterminal both have three beams in the DL will be described by way ofexample. A base station may be the base station 110 of FIG. 1 . Aterminal may be the terminal 120 of FIG. 1 .

Referring to FIG. 5 , the terminal 120 may perform beamformingcommunication with the base station 110. An example of DL will bedescribed. The base station 110 may transmit signals by using multiplebeams (e.g., a first transmission beam 511, a second transmission beam512, and a third transmission beam 513) in order to identify an optimalbeam of the base station 110. The terminal 120 may receive signals byusing multiple beams (e.g., a first reception beam 521, a secondreception beam 522, and a third reception beam 523) in order to identifyan optimal beam of the terminal 120. Hereinafter, a procedure fortransmitting or receiving a signal while changing a beam may be referredto as “beam tracking,” “beam search,” “direction search,” “directionsweeping,” or “direction training.”

The base station 110 may acquire channel qualities of the beams of thebase station 110, and may identify an optimal transmission beam. Theterminal 120 may acquire channel qualities of the beams of the terminal120, and may identify an optimal reception beam. The channel quality ofa beam signifies the channel quality of a signal transmitted or receivedusing a beam.

In the disclosure, a signal transmitted or received using a beam may bea synchronization signal or a reference signal. For example, asynchronization signal may include at least one of a primary SS (PSS), asecondary SS (SSS), an extended SS (ESS), and an SS block. Also, forexample, a reference signal may include at least one of a beam RS (BRS),a beam refinement RS (BRRS), a cell-specific RS (CRS), a channel stateinformation-RS (CSI-RS), and a DM-RS.

In the disclosure, channel quality may be at least one of, for example,beam reference signal received power (BRSRP), reference signal receivedpower (RSRP), reference signal received quality (RSRQ), received signalstrength indicator (RSRI), signal to interference and noise ratio(SINR), carrier to interference and NR (CINR), signal to NR (SNR), errorvector magnitude (EVM), bit error rate (BER), and block error rate(BLER). It goes without saying that, besides the above-describedexample, other terms having equivalent technical meanings or othermetrics indicating channel quality may be used. Hereinafter, in thedisclosure, high channel quality signifies a case in which a signalmagnitude-related channel quality value is large or an errorrate-related channel quality value is small. High channel quality maysignify that a smooth wireless communication environment is ensured aschannel quality becomes higher. Also, an optimal beam may signify a beamhaving the highest channel quality among beams.

The base station 110 may identify the second transmission beam 512 as anoptimal DL transmission beam. The terminal 120 may identify the secondreception beam 522 as an optimal DL reception beam. The terminal 120 mayacquire synchronization for a second link 532 formed by the secondtransmission beam 512 and the second reception beam 522.

The terminal 120 may acquire an offset 550 which is a difference betweena reference time and a cell time of the terminal 120. A reference timesignifies a reference of an actual cell time of the base station 110.That is, the offset 550 signifies a time difference between the basestation 110 and the terminal 120 which is caused by a physical distancetherebetween. The term “offset” may be referred to as a “clock skew.”The terminal 120 may acquire initial synchronization with the basestation 110 by applying the offset 550 to a subsequently-acquired celltime of the terminal 120 (as indicated by reference numeral 560).

Even when the offset 550 is applied, subsequently-acquiredsynchronization may be different from the initial synchronization, dueto the performance of hardware (e.g., a timer) of the terminal 120, astate change (e.g., temperature, time, or pressure) of the terminal 120,and the like. For example, an oscillator configured to generate a clockis slightly affected by a state change, such as temperature or pressure,and thus an error between synchronizations may occur. In order to tracksynchronization, the terminal 120 may determine a synchronizationvariance which is a difference between subsequently-acquiredsynchronization and previous synchronization. The term “synchronizationvariance” may be referred to as a “clock drift,” a “synchronizationerror,” a “synchronization deviation,” or the like.

The terminal 120 may update synchronization information (e.g., anoffset, an expected cell time, and a synchronization range) (asindicated by reference numeral 570) by applying the synchronizationvariance in a subsequently-acquired cell time of the terminal 120 (asindicated by reference numeral 580). A procedure for updatingsynchronization information so as to prevent the occurrence of failureof synchronization with the base station 110 is referred to as a“synchronization tracking procedure.” The terminal 120 may updatesynchronization information so that the acquired cell time can belocated in a synchronization range. The term “synchronization range”refers to an effective range of a cell time used for the terminal 120 toidentify whether synchronization with the base station 110 fails. Thelength of a synchronization range may be configured according to thelength of a CP or the performance of a synchronization timer of theterminal 120.

According to a change in a physical path, a propagation time of a signalalso changes. Synchronization is changed according to a propagation timeof a signal, and thus may be dependent on a physical path. In order totrack the acquired synchronization, the terminal 120 may schedule thesecond reception beam 522 which is a serving beam.

When the terminal 120 moves or rotates, due to the directivity propertyof beamforming communication, an optimal beam-pair link between the basestation 110 and the terminal 120 may be changed from the second link 532to another link (e.g., a first link 531 or a third link 533). Also, whena moving object enters the second link 532 or a wireless channel betweenthe base station 110 and the terminal 120 is changed, the second link532 may no longer be an optimal beam-pair link between the base station110 and the terminal 120. In consideration of the mobility of theterminal 120 or a channel change, the base station 110 or the terminal120 is required to transmit or receive a signal while continuouslychanging a beam.

The terminal 120 may receive a first signal by using the first receptionbeam 521. The terminal 120 may schedule the first reception beam 521during a first interval in which the terminal 120 receives the firstsignal. The terminal 120 may receive a second signal by using the secondreception beam 522. The terminal 120 may schedule the second receptionbeam 522 during a second interval in which the terminal 120 receives thesecond signal. The terminal 120 may receive a third signal by using thethird reception beam 523. The terminal 120 may schedule the thirdreception beam 523 during a third interval in which the terminal 120receives the third signal.

When the terminal 120 fairly schedules all of the beams of the terminal120, the number of times of scheduling of a serving beam (e.g., thesecond reception beam 522) may be relatively reduced. As the number oftimes of scheduling of the serving beam is reduced, the opportunity forsynchronization tracking on a path of the serving beam is reduced, andthus the probability of out-of-synchronization may increase. Incontrast, when the terminal 120 relatively frequently schedules aserving beam in order to perform synchronization tracking, theopportunity for measuring qualities of neighboring beams (e.g., thefirst reception beam 521 and the third reception beam 523) other thanthe serving beam is reduced, and thus it is difficult to instantaneouslyreflect a change in a channel state. Accordingly, in order toefficiently solve the above-described problems, the terminal 120 isrequired to schedule a beam by considering synchronization tracking andbeam tracking together.

The terminal 120 may perform operations for interworking betweenbeam-based synchronization tracking and beam tracking. The terminal 120may perform synchronization while performing beam tracking. Hereinafter,in the disclosure, a cycle, in which beam tracking of all beams isperformed to update a serving beam, may be referred to as a “beamforminginterval,” an “interworking interval,” or the like. Hereinafter,operations of a terminal for interworking between synchronizationtracking and beam tracking will be described with reference to FIGS. 6to 12, 13A, 13B, 13C, 14, 15A, 15B, 15C, 16, and 17 .

FIG. 6 is a flowchart illustrating an operation of a terminal forinterworking between synchronization tracking and beam trackingaccording to various embodiments of the disclosure. FIG. 6 illustratesan example of an operating method of the terminal 120.

Referring to FIG. 6 , in operation 601, the terminal may acquiresynchronization information of a first beam. The first beam may be aserving beam. The term “serving beam” refers to the most appropriatebeam for communication with a base station among beams of the terminalor a beam which is currently being used to communicate with the basestation thereamong. The terminal may identify a serving beam based onthe channel quality of each of beams of the terminal. Synchronizationinformation may be parameters for determination of successfulsynchronization between the base station and the terminal. For example,synchronization information may be a cell time. Also, for example,synchronization information may be an offset of a cell time. Theterminal may acquire initial synchronization to a relevant cell based onsynchronization signals received from the base station. In a beamformingcommunication system, the terminal communicates with the base station byusing the serving beam, and thus may acquire initial synchronization ofthe serving beam.

In operation 603, the terminal may update the synchronizationinformation of the first beam. In this example, the update ofsynchronization information signifies synchronization tracking. Theterminal may track a synchronization variance which occurs due to achannel change or the performance of the terminal itself. The terminalmay determine a synchronization variance whenever performingsynchronization tracking. The terminal may determine a synchronizationvariance based on previous synchronization information andsynchronization information acquired at the current stage. For example,the terminal may determine a difference between a previous cell time ofa beam and a current cell time of the beam. The terminal may determinethe difference between the cell times as a synchronization variance. Theterminal may compensate for a cell time offset (CTO) by thesynchronization variance. The terminal may update a synchronizationrange by using the compensated offset. That is, the terminal maydetermine a synchronization range by using the synchronization varianceso as to maintain synchronization with the base station.

According to various embodiments, the terminal may update thesynchronization information of the serving beam. A propagation time of asignal is changed according to a physical path along which a signal istransmitted between the base station and the terminal, and thussynchronization is dependent on the physical path. The terminal performswireless communication along a path formed through the serving beam andmay update the synchronization information of the serving beam. In someembodiments, the terminal may update synchronization information byusing a serving beam. For example, the terminal may update the acquiredsynchronization information based on the first beam. In order to updatesynchronization information, the terminal may schedule the first beamwhich is a serving beam. The terminal may acquire a synchronizationvariance of the first beam by receiving a signal by using the firstbeam. The terminal may update synchronization information based on thesynchronization variance of the serving beam.

In some other embodiments, the terminal may update synchronizationinformation by using a neighboring beam as well as a serving beam. Forexample, the terminal may acquire a value of a synchronization varianceof the second beam by receiving a signal by using a second beam which isa neighboring beam. The terminal may acquire a value of asynchronization variance according to the difference betweensynchronization information of the second beam, acquired during aprevious beam training interval, and the synchronization information ofthe second beam acquired in operation 603. The terminal may update thesynchronization of the first beam, which is s serving beam, based on thesynchronization variance of the second beam which is a neighboring beam.

In operation 605, the terminal may determine channel quality of at leastone second beam. The at least one second beam may be a beam differentfrom the first beam in operation 601. The at least one second beam maybe a neighboring beam. The terminal may determine channel qualities ofsignals received using neighboring beams.

According to various embodiments, the terminal may determine at leastone channel quality based on synchronization information updated inoperation 603. Signals used to determine channel quality may be signalstransmitted by the base station. In order to compare channel quality ofthe at least one second beam with that of the serving beam, the terminalmay be required to receive signals in a state where synchronization withthe base station is acquired. The terminal may receive signals based onthe latest synchronization information. For example, the base stationmay periodically transmit BRSs. The terminal may determine channelquality of each of the at least one second beam by receiving BRSs byusing each of the at least one second beam. That is, the terminal mayperform a procedure for receiving signals by using neighboring beams anddetermining channel qualities, that is, a beam tracking procedure.

According to various embodiments, the terminal may configure the numberof the at least one second beam. For example, the terminal may determinethe number of the at least one second beam to be a fixed number (e.g.,3). The terminal may schedule three beams among the neighboring beams.As another example, the terminal may determine the number of the atleast one second beam to be a variable number. The terminal mayadaptively determine the number of the at least one second beam amongthe neighboring beams based on a channel change. In some embodiments,the number of the at least one second beam to be variably is determinedbased on a channel change.

In operation 607, the terminal may update the serving beam based on thechannel quality. The terminal may determine channel quality of the firstbeam. As an example, the terminal may determine channel quality of thefirst beam when receiving a signal in order to update synchronizationinformation in operation 603. As another example, the terminal maydetermine channel quality by additionally receiving a signal by usingthe first beam.

The terminal may determine channel qualities of neighboring beams. Thechannel qualities of the neighboring beams may include the channelquality of the at least one second beam in operation 605. According toan embodiment, the terminal may additionally receive a signal by usinganother neighboring beam as well as the at least one second beam, andmay determine channel quality of the signal.

According to various embodiments, the terminal may update a serving beambased on channel quality of the serving beam and channel qualities ofneighboring beams. For example, the terminal may determine, as a servingbeam, one of neighboring beams having channel qualities higher than thatof the first beam which is a current serving beam. The terminal maychange a serving beam from the first beam to one of the neighboringbeams. As another example, the terminal may determine channel quality ofthe first beam to be higher than channel qualities of all theneighboring beams. The terminal may maintain a serving beam as the firstbeam.

According to various embodiments, the terminal may update a serving beambased on channel quality of the first beam and channel quality of the atleast one second beam. The terminal may also update a serving beam bycomparing channel quality of the first beam with channel quality of theat least one second beam which is some beams rather than all theneighboring beams of the terminal. The terminal updates a serving beamis updated before determining channel qualities of all the beams forbeam tracking, and thus can adapt more quickly to a channel.

Although not illustrated in FIG. 6 , according to various embodiments,the terminal may repeatedly and additionally perform a synchronizationtracking procedure in operation 603 and a beam tracking procedure inoperation 605. Also, the terminal may repeatedly perform operation 605until channel qualities of all the neighboring beams are determined.Such a repeated procedure will be described below in detail withreference to FIGS. 7 to 12, 13A, 13B, 13C, 14, 15A, 15B, 15C, and 16 .

The terminal performs beam tracking after synchronization tracking, andthus can obtain a more accurate measurement result than in the case ofbeam tracking. Since a synchronization tracking result is reflected, theaccuracy of measurement of a neighboring beam can be improved. When aserving beam is used during synchronization tracking and a neighboringbeam is scheduled during beam tracking, a ratio of the number of beamsscheduled during the synchronization tracking to that of beams scheduledduring the beam tracking may affect communication performance.Hereinafter, FIG. 7 illustrates the flow of an operation of a terminalfor performing interworking between synchronization tracking and beamtracking by controlling a ratio of a serving beam (e.g., a first beam)scheduled during the synchronization tracking to neighboring beams(e.g., at least one second beam) used during the beam tracking. FIG. 8illustrates the flow of an operation of a terminal for performinginterworking between synchronization tracking and beam tracking bycontrolling a ratio of a serving beam (e.g., a first beam) scheduledduring the synchronization tracking to neighboring beams (e.g., at leastone second beam) used during the beam tracking. FIG. 9 illustrates theflow of an operation of a terminal for performing interworking betweensynchronization tracking and beam tracking by controlling a ratio of aserving beam (e.g., a first beam) scheduled during the synchronizationtracking to neighboring beams (e.g., at least one second beam) usedduring the beam tracking.

Ratio-Based Interworking

FIG. 7 is a flowchart illustrating an operation of a terminal for fixedinterworking between serving-beam-based synchronization tracking andbeam tracking according to various embodiments of the disclosure. FIG. 7illustrates an example of an operating method of the terminal 120.

Referring to FIG. 7 , in operation 701, the terminal may acquiresynchronization. The terminal may acquire synchronization of a servingbeam. The terminal may receive a signal by using the serving beam andmay acquire synchronization information of the received signal. Theterminal may determine initial synchronization. Operation 701corresponds to operation 601 of FIG. 6 , and thus a detailed descriptionof the overlapping configuration will be omitted.

In operation 703, the terminal may perform synchronization tracking. Theterminal may perform synchronization tracking using the serving beam.Hereinafter, synchronization tracking performed using a serving beam maybe referred to as “serving-beam-based synchronization tracking.”

The terminal may schedule the serving beam. The terminal may receive asignal by using the scheduled serving beam. The terminal may receive asignal by using the scheduled serving beam so as to performsynchronization. The terminal may receive a signal so as to determine acell time of the serving beam. The terminal may use the cell time todetermine a synchronization variance of the initial synchronizationacquired in operation 701. The terminal may compensate for thesynchronization variance so as to perform serving-beam-basedsynchronization tracking. Also, when a cycle is repeated according tothe determination in operation 707, the terminal may determine asynchronization variance of previous synchronization information (e.g.,a cell time).

Hereinafter, for convenience of description, a time for which a servingbeam is scheduled, that is, a time for which a signal is received usinga serving beam, may be referred to as a “synchronization interval.”According to an embodiment, a synchronization interval may have a lengthof 5 ms. A base station may configure the serving beam as a receptionbeam during a synchronization interval so as to receive synchronizationsignals.

In operation 705, the terminal may perform beam tracking based on afixed ratio. The term “ratio” in fixed ratio may refer to the number ofscheduled neighboring beams relative to a serving beam in one trackingcycle. The term “tracking cycle” refers to a cycle in whichsynchronization tracking is performed. A tracking cycle may include asynchronization interval. A tracking cycle may include a beam trackinginterval as well as a synchronization interval. The terminal mayschedule at least one neighboring beam during a beam tracking interval.The term “fixed ratio” refers to a fixed ratio of scheduling ofneighboring beams relative to scheduling of a serving beam in eachtracking cycle during multiple tracking cycles in which measurement ofall the neighboring beams is to be performed. For example, a fixed ratioof 3 implies that three neighboring beams are scheduled when a servingbeam is scheduled once.

According to various embodiments, a fixed ratio may be fixed accordingto the performance of hardware of the terminal or the design of theterminal. For example, a value of a fixed ratio may be determinedaccording to an error range of a timer for synchronization tracking ofthe terminal. When an error range of the timer is in a designated range,a value of a fixed ratio may be determined as a value corresponding tothe designated range.

According to various embodiments, a fixed ratio may be differentlyconfigured whenever a serving beam is updated. For example, a fixedratio may be determined based on the number of beams operated for beamtracking. The number of beams operated for beam tracking may bedifferently configured in each serving beam updating cycle. As anotherexample, a fixed ratio may be configured according to the degree (e.g.,a synchronization variance or an offset) of synchronization trackingusing a serving beam updated whenever the serving beam is updated.

The terminal may schedule neighboring beams in order so as to receive asignal by using a relevant beam. The terminal may determine channelquality of a scheduled beam by measuring quality of the received signal.The terminal may determine channel qualities of neighboring beams. Forexample, when a fixed ratio is 3, the terminal may determine channelqualities of three neighboring beams.

In operation 707, the terminal may determine whether beam tracking ofall the beams has been performed. All the beams may include a servingbeam and neighboring beams configured for beam tracking. A result of thebeam tracking of the serving beam may be acquired by receiving a signalin operation 703. The terminal may determine whether a result of thebeam tracking (e.g., channel quality) of each of neighboring beams hasbeen acquired. When the beam tracking of all the beams has beenperformed, the terminal may perform operation 709. When there exists abeam of which beam tracking has not been performed, the terminal mayagain perform operation 703.

In operation 709, the terminal may update the serving beam. The terminalmay determine whether there exists channel quality of a beam which ishigher than the channel quality of the serving beam among the channelqualities of the neighboring beams. When there exists channel quality ofa beam which is higher than the channel quality of the serving beamamong the channel qualities of the neighboring beams, the terminal maydetermine the relevant beam as a serving beam. When there exists nochannel quality of a beam which is higher than the channel quality ofthe serving beam among the channel qualities of the neighboring beams,the terminal may maintain the existing serving beam.

In FIG. 7 , the terminal schedules the neighboring beams at the fixedratio, and thus can previously perform scheduling of all the beams forperforming beam tracking. The terminal determines channel quality andperforms a storage operation according to the fixed ratio, and thus thecomplexity of calculation in the terminal can be reduced. In the case ofa static or stable channel, an effect of interworking betweensynchronization tracking and beam tracking can be maximized through thefixed interworking described with reference to FIG. 7 .

FIG. 8 is a flowchart illustrating an operation of a terminal foradaptive interworking between serving-beam-based synchronizationtracking and beam tracking according to various embodiments of thedisclosure. FIG. 8 illustrates an example of an operating method of theterminal 120.

Referring to FIG. 8 , in operation 801, the terminal may acquiresynchronization. Operation 801 corresponds to operation 701 of FIG. 7 ,and thus a detailed description of the overlapping configuration will beomitted.

In operation 803, the terminal may determine a tracking ratio. Atracking ratio has a meaning in contrast with that of a fixed ratio, andsignifies a ratio of scheduling of neighboring beams relative toscheduling of a serving beam in one tracking cycle. That is, a trackingratio signifies a ratio of beam tracking relative to synchronizationtracking. In this example, a tracking ratio may be changed in eachtracking cycle. The terminal may change a tracking ratio in eachtracking cycle during multiple tracking cycles in which measurement ofall the neighboring beams is performed. That is, the terminal maydetermine a tracking ratio whenever operation 803 is repeatedlyperformed according to the determination in operation 809.

During a first tracking cycle, the terminal may set a tracking ratio toa default value. As an example, a default value may be a constant, suchas 3. As another example, a default value may be the value of a trackingratio finally used when a previous reception beam is swept.

According to various embodiments, the terminal may determine a trackingratio in each tracking cycle. The terminal may determine a trackingratio based on information acquired in one tracking cycle. In someembodiments, the terminal may determine a tracking ratio based on aresult of the synchronization tracking. For example, the terminal maydetermine a tracking ratio according to a value of a synchronizationvariance during synchronization tracking. When a synchronizationvariance is large, the synchronization variance exceeds a CP and theprobability of out-of-synchronization becomes higher. Therefore, theterminal may reduce a tracking ratio. According to a reduction in atracking ratio, a ratio of scheduling of a serving beam relative toscheduling of neighboring beams becomes higher, and thus the terminalcan more accurately control synchronization.

In some embodiments, the terminal may determine a tracking ratio basedon channel quality. The terminal may receive a signal by using a servingbeam or a neighboring beam so as to determine channel quality of theserving beam. For example, in operation 805, when synchronizationtracking is performed, the terminal may receive a signal by using aserving beam so as to determine RSRP of the serving beam. As a varianceof channel quality becomes larger, a synchronization variance mayincrease. In this example, the terminal may increase a ratio ofscheduling of a serving beam relative to scheduling of neighboringbeams. According to an embodiment, a variance of channel quality may bemeasured through a neighboring beam as well as a serving beam. A servingbeam and a neighboring beam are not identical to each other, but changetrends of the serving beam and the neighboring beam adjacent to theserving beam may be similar to each other. Also, when channel quality ofthe serving beam is lower than or equal to a threshold, the terminal maybe required to more quickly identify another optimal reception beam. Inthis example, the terminal may increase a ratio of scheduling ofneighboring beams relative to scheduling of a serving beam.

In some other embodiments, the terminal may differently determine atracking ratio according to the number of neighboring beams. Theterminal may update a serving beam in each designated cycle.Accordingly, the terminal may determine a tracking ratio based on atleast one of the number of neighboring beams which is measurable in adesignated cycle, the number of all the neighboring beams configured forbeam tracking, and the number of neighboring beams of which channelqualities are currently determined.

In addition, the terminal may combine at least two of differentconditions for determination of the tracking ratio so as to determine atracking ratio. For example, the terminal may determine a tracking ratiobased on channel qualities of at least some of neighboring beams, andmay determine a tracking ratio based on the number of some other beamsand a remaining time in a designated cycle. As another example, theterminal may determine a tracking ratio based on channel quality and asynchronization variance.

In operation 805, the terminal may perform synchronization tracking.Operation 805 corresponds to operation 703 of FIG. 7 , and thus adetailed description of the overlapping configuration will be omitted.

In operation 807, the terminal may perform beam tracking based on thetracking ratio. The terminal may perform beam tracking according to thetracking ratio determined in operation 803. For example, when thetracking ratio determined in operation 803 is 5, the terminal mayschedule five neighboring beams. The terminal may perform beam trackingduring a beam tracking interval according to the tracking ratio. A beamtracking interval may be different in each tracking cycle.

The terminal may schedule beams in order by the number of beams based onthe tracking ratio so as to receive a signal by using each of therelevant beams. The terminal may measure quality of the received signalso as to determine channel quality of the scheduled beam. The terminalmay determine channel qualities of neighboring beams. For example, whena tracking ratio is 5, the terminal may determine channel qualities offive neighboring beams.

In operation 809, the terminal may determine whether beam tracking ofall the beams has been performed. Operation 809 corresponds to operation707 of FIG. 7 , and thus a detailed description of the overlappingconfiguration will be omitted. When the beam tracking of all the beamshas been performed, the terminal may perform operation 811. When thereexists a beam of which beam tracking has not been performed, theterminal may again perform operation 803.

In operation 811, the terminal may update the serving beam. Operation811 corresponds to operation 709 of FIG. 7 , and thus a detaileddescription of the overlapping configuration will be omitted.

Although a tracking ratio is illustrated in FIG. 8 as being determinedbefore synchronization tracking, according to an embodiment, a trackingratio may be determined after synchronization tracking. In other words,the terminal may perform operation 805 before operation 803. In thisexample, the terminal may determine a tracking ratio by using moreaccurate synchronization information.

In FIG. 8 , differently from FIG. 7 , the terminal may determine atracking ratio in each tracking cycle and may control scheduling ofneighboring beams for beam tracking according to the tracking ratio, soas to perform interworking between channel-based synchronizationtracking and beam tracking. In a situation where a channel is suddenlychanged or in the case of a channel on which a communication state isunstable, a terminal can maximize an effect of interworking betweensynchronization tracking and beam tracking through the adaptiveinterworking described with reference to FIG. 8 .

FIG. 9 illustrates an example of fixed interworking betweenserving-beam-based synchronization tracking and beam tracking accordingto various embodiments of the disclosure. A time duplex division schemewill be described as example of beam scheduling for performingsynchronization tracking and beam tracking.

Referring to FIG. 9 , a terminal may perform synchronization trackingand beam tracking. A fixed ratio may be 3. The terminal may schedulebeam #X, which is a serving beam, during a first synchronizationinterval 910. Consideration is given to a situation in whichsynchronization of beam #X has been acquired. The terminal may receive asignal by using beam #X during the first synchronization interval 910 soas to determine synchronization information (e.g., a cell time, anoffset, and a synchronization range) of beam #X. The terminal maydetermine a synchronization variance based on previously-acquiredsynchronization information and the synchronization information acquiredduring the first synchronization interval 910. The terminal maycompensate for a synchronization variance so as to updatesynchronization information during the first synchronization interval910. For example, the terminal may update an offset of beam #X byapplying a synchronization variance so that the offset thereof cancoincide with a cell time acquired during initial synchronization.Thereafter, the terminal may switch a beam from the serving beam (beam#X) to a neighboring beam.

The terminal may sequentially schedule beam #1, beam #2, and beam #3,which are three neighboring beams, during a first beam tracking interval920. The terminal may perform beam switching. The terminal may performbeam switching so as to sequentially form a beam in each measurementunit interval. The terminal may receive a signal by using each of thescheduled beams so as to determine channel quality of each of thescheduled beams. In order to update the serving beam, the terminal maystore information on the determined channel qualities. The terminal maystore information on the neighboring beams until beam tracking of allthe beams is terminated.

The terminal may schedule beam #X, which is a serving beam, during asecond synchronization interval 930. The terminal may update thesynchronization information of beam #X in the first synchronizationinterval 910. For example, the terminal may again determine a value of asynchronization variance of beam #X during the second synchronizationinterval 930. The terminal may update the offset of beam #X according tothe value of the synchronization variance of beam #X determined duringthe second synchronization interval 930. The terminal may sequentiallyschedule beam #4, beam #5, and beam #6, which are three neighboringbeams, during a second beam tracking interval 940.

The terminal may again schedule beam #X, which is a serving beam, duringa third synchronization interval 950. As described above, the terminalmay perform synchronization tracking and beam tracking during asynchronization interval and a beam tracking interval for threeneighboring beams which are repeated by turns, respectively. Onesynchronization interval and one beam tracking interval may be referredto as “one tracking cycle.” Until the terminal performs beam tracking ofall the beams, a tracking cycle may be repeated. For example, when thenumber of beams for beam tracking is 40 in total, the terminal mayperform synchronization tracking and beam tracking during a total of 13tracking cycles (40=3×13+1).

Interworking Between any-Beam-Based Synchronization Tracking and BeamTracking

FIG. 10 is a flowchart illustrating an operation of a terminal forinterworking between any-beam-based synchronization tracking and beamtracking according to various embodiments of the disclosure. FIG. 10illustrates an example of an operating method of the terminal 120.

Referring to FIG. 10 , in operation 1001, the terminal may acquiresynchronization. Operation 1001 corresponds to operation 701 of FIG. 7 ,and thus a detailed description of the overlapping configuration will beomitted.

In operation 1003, the terminal may perform beam scheduling. Theterminal may schedule one of beams thereof. In this example, beams ofthe terminal signify beams of the terminal for beam tracking. In orderto repeatedly perform operations 1003 to 1005 according to operation1009 described below, the terminal may sequentially schedule the beams.That is, differently from FIGS. 7, 8, and 9 in which a serving beam andneighboring beams are illustrated as being repeatedly switched in turn,the terminal may perform scheduling regardless of whether acurrently-scheduled beam is a serving beam. That is, the terminal mayschedule any beam.

The terminal may repeat beam scheduling by using various patterns. Insome embodiments, the terminal may schedule a beam so as to perform beamsweeping according to a predefined pattern regardless of a serving beam.By using a predefined pattern, the complexity of calculation can bereduced. In some other embodiments, the terminal may first schedule aserving beam, and then may sequentially sweep neighboring beams in asubsequent repeated cycle. A serving beam is first scheduled, and thusthe accuracy of synchronization tracking described below can be furtherimproved.

In operation 1005, the terminal may perform scheduled-beam-basedsynchronization tracking. The terminal may receive a signal by using thebeam scheduled (hereinafter “scheduled beam”) in operation 1003. In thisexample, the scheduled beam is any beam and may be a serving beam or aneighboring beam. Scheduled-beam-based synchronization tracking may bereferred to as “any-beam-based synchronization tracking.”

The terminal may receive a signal by using the scheduled beam. Theterminal may determine synchronization information of the receivedsignal. The terminal may compare previous synchronization information ofthe relevant scheduled beam with the determined synchronizationinformation thereof. The terminal may determine, as a synchronizationvariance, the difference between the previous synchronizationinformation of the relevant scheduled beam and the determinedsynchronization information thereof. Such a synchronization variance maybe caused by the state (e.g., temperature or pressure) of the terminalwith the passage of time or the performance of the terminal (e.g., thereception performance of the terminal or the performance of a clockwithin the terminal). For a serving beam and a neighboring beam,absolute synchronizations are different due to a physical distancedifference, but synchronization variances may be identical or similar toeach other. Causes of a synchronization variance are not beam-specific.The terminal may update synchronization information of a serving beambased on the synchronization variance. Although the terminal does notnecessarily schedule the serving beam, the terminal may acquire asynchronization change of a neighboring beam so as to update thesynchronization information of the serving beam. In a first cycle, theterminal may compensate initial synchronization acquired in operation1001 for a synchronization variance so as to update synchronizationinformation. In a subsequent cycle, the terminal may compensate thesynchronization information, updated in the previous cycle, for asynchronization variance so as to update synchronization information.

In some embodiments, the terminal may update synchronization informationby using values of multiple synchronization variances. The terminal maydetermine an estimated value of a synchronization variance based on thesynchronization variances obtained whenever a cycle is repeated. Forexample, the terminal may average synchronization variances so as todetermine an estimated value of a synchronization variance. As anotherexample, the terminal may apply weights of respective beams to averagesynchronization variances so as to determine an estimated value of asynchronization variance. A weight may be determined based on channelquality. The terminal may compensate for the estimated value of thesynchronization variance so as to update synchronization information.

In some other embodiments, the terminal may not update synchronizationinformation in at least one cycle. Whenever a cycle is repeated, theterminal may calculate synchronization variances. When the number ofsynchronization variances is larger than or equal to a predeterminedvalue, the terminal may determine an estimated value of asynchronization variance based on the synchronization variances. Theterminal can improve the reliability of synchronization tracking byconsidering multiple synchronization variances of multiple beams.

In operation 1007, the terminal may perform scheduled-beam-based beamtracking. The terminal may receive a signal by using the beam scheduledin operation 1003. The terminal may determine channel quality of thereceived signal. For example, the terminal may determine BRSRP. Theterminal may determine channel quality as channel quality of thescheduled beam. According to various embodiments, the terminal may storeinformation on channel quality of the scheduled beam (hereinafter “beaminformation”), for comparison with the channel quality determined inanother cycle.

Operations 1003 to 1007 are repeated according to operation 1009described below, and thus the terminal may determine channel qualitiesof all the beams for beam tracking. A scheme for scheduling any beam andsequentially performing synchronization tracking and beam trackingaccording to the scheduled beam as in operations 1003 to 1007 may bereferred to as an “any-beam-based interworking procedure.” The terminalmay repeatedly perform an any-beam-based interworking procedure so as todetermine channel qualities of all the beams for tracking.

In operation 1009, the terminal may determine whether beam tracking ofall the beams has been performed. Operation 1009 corresponds tooperation 707 of FIG. 7 , and thus a detailed description of theoverlapping configuration will be omitted. When the beam tracking of allthe beams has been performed, the terminal may perform operation 1011.When there exists a beam of which beam tracking has not been performed,the terminal may again perform operation 1003.

In operation 1011, the terminal may update the serving beam. Operation1011 corresponds to operation 709 of FIG. 7 , and thus a detaileddescription of the overlapping configuration will be omitted.

FIG. 11 is a flowchart illustrating an operation of a terminal forbeam-based synchronization tracking according to various embodiments ofthe disclosure. FIG. 11 illustrates an example of an operating method ofthe terminal 120. A beam-based synchronization tracking procedure ofFIG. 11 may correspond to operation 703 of FIG. 7 , operation 805 ofFIG. 8 , and operation 1005 of FIG. 10 .

Referring to FIG. 11 , in operation 1101, the terminal may determinewhether a serving-beam-based synchronization tracking function isactivated. When the serving-beam-based synchronization tracking functionis activated, the terminal may perform synchronization tracking by usinga serving beam. When the serving-beam-based synchronization trackingfunction is not activated, the terminal may perform synchronizationtracking by using any beam regardless of whether any beam is a servingbeam. Any beam may be a serving beam or a neighboring beam. That is, theterminal may perform synchronization tracking according to anany-beam-based synchronization tracking scheme. When theserving-beam-based synchronization tracking function is activated, theterminal may perform operation 1103. When the serving-beam-basedsynchronization tracking function is not activated, the terminal mayperform operation 1107.

In operation 1103, the terminal may determine whether a scheduled beamis a serving beam. When the scheduled beam is a serving beam, theterminal may not perform separate beam scheduling. Accordingly, theterminal may perform operation 1107. When the scheduled beam is not aserving beam, the terminal may perform operation 1105 so that theterminal can use a serving beam. In operation 1105, the terminal mayschedule a serving beam.

In operation 1107, the terminal may acquire a peak. The terminal mayacquire a peak of a currently-scheduled beam. The terminal may receive asignal by using the scheduled beam. The terminal may perform correlationcalculation on the signal. Specifically, the terminal may performcorrelation calculation between a candidate sequence of a signal and asequence (e.g., a synchronization sequence) of the actually-receivedsignal. In order to determine a reception time point of an actual signalin a designated range, the terminal may repeatedly perform correlationcalculation. According to a result of the correlation calculation, theterminal may determine correlation values depending on the level atwhich the two sequences coincide with each other. The terminal mayacquire a correlation value of the peak. For example, among thecorrelation values, the terminal may acquire a peak correlation valuelarger than or equal to a correlation threshold or the largest peakcorrelation value. A time point of detection of a peak correlation valueis a time point of reception of a sequence of an expected signal. Theterminal may determine a time point of acquisition of a peak, that is, atime point of detection of a peak correlation value. A position ofdetection of a peak correlation value may be referred to as a “SS peakposition.”

When the scheduled beam is a serving beam, the terminal may acquire apeak of the serving beam. The terminal may acquire a peak of the servingbeam, from updated synchronization information or synchronizationinformation of a serving beam acquired after initial synchronization.When the scheduled beam is not a serving beam, the terminal may acquirea peak of a neighboring beam. During any-beam-based synchronizationtracking, the terminal may store synchronization information of aneighboring beam as well as a serving beam, and may calculate asynchronization variance. The terminal may acquire a peak of aneighboring beam by using pieces of pre-stored synchronizationinformation of neighboring beams.

In operation 1109, the terminal may perform filtering. In this example,the term “filtering” refers to filtering of interference to aneighboring cell. During any-beam-based synchronization tracking, theterminal may schedule not only a beam corresponding to a serving beambut also a beam corresponding to a neighboring beam. Accordingly, when ascheduled neighboring beam is oriented to a neighboring cell, theterminal may detect a peak of a synchronization signal transmitted fromthe neighboring cell.

FIG. 12 illustrates an example of interference during any-beam-basedsynchronization tracking according to various embodiments of thedisclosure.

Referring to the example illustrated in FIG. 12 , the terminal 120 mayperform any-beam-based synchronization tracking and beam tracking.

FIG. 12 illustrates a situation in which a serving beam for the terminal120 is a beam 1221 and a serving beam for the base station 110 is a beam1211. That is, a current optimal beam-pair link is a link 1250 accordingto various embodiments of the disclosure. In order to performany-beam-based synchronization tracking, the terminal 120 may schedulenot only the serving beam 1221 but also a neighboring beam 1222.

When the terminal 120 receives a signal from the base station 110through the neighboring beam 1222, a neighboring base station 1210 maytransmit a synchronization signal by using a beam 1213. In this example,a link 1260 which may be formed by the beam 1213 and the beam 1222 mayprovide channel quality higher than that of a link (not illustrated)which may be formed with the base station 110 through the beam 1222.Accordingly, the terminal may also acquire a peak of the neighboringbase station 1210. In particular, when a neighboring beam is scheduledduring any-beam-based synchronization tracking, the terminal may morestrongly receive a signal from a neighboring cell than in a case where aserving beam is scheduled during serving-beam-based synchronizationtracking. Accordingly, in order to acquire a peak of a cell currentlybeing accessed, the terminal may perform filtering.

According to various embodiments, the terminal may apply definedfiltering rules so as to perform filtering. Embodiments of the definedfiltering rules will be described below in detail with reference toFIGS. 13A and 13B.

In operation 1111, the terminal may calculate a synchronizationvariance. The terminal may determine a difference between a first celltime of a scheduled beam in a previous cycle (e.g., a beamforminginterval) and a second cell time of a scheduled beam in a current cycle.The terminal may calculate a synchronization variance according to thedifference between the first cell time and the second cell time. In thisexample, it should be noted that a cell time does not need to be a celltime of a serving beam. A cell time may be a cell time of a neighboringbeam. Also, a synchronization variance may be a synchronization varianceof a serving beam or a synchronization variance of a neighboring beam.

In operation 1113, the terminal may apply the synchronization varianceso as to perform synchronization tracking. A synchronization variance isirrelevant to whether a main cause of a synchronization change is aserving beam or a neighboring beam, and thus may have identical orsimilar change trends. Accordingly, the terminal may performsynchronization tracking according to a synchronization variance of aneighboring beam as well as a synchronization variance of a servingbeam.

The terminal may update synchronization information by thesynchronization variance. For example, the terminal may compensate foran offset of a cell time (hereinafter “cell time offset”) by thesynchronization variance. When a synchronization variance is 3, a valueof a cell time offset may be increased by three. The terminal maycompensate for a cell time offset so as to update a synchronizationrange for determination of synchronization success.

According to various embodiments, the terminal may apply not only asynchronization variance of a scheduled beam but also synchronizationvariances of other beams so as to perform synchronization tracking. Theterminal may apply multiple synchronization variances so as to updatesynchronization information. For example, the terminal may take anaverage on synchronization variances so as to update synchronizationinformation. As another example, the terminal may apply a weight to eachof synchronization variances so as to update synchronizationinformation. Additionally, the terminal may identify at least some ofsynchronization variances, and may take an average on the at least somesynchronization variances or may apply a weight to each of the at leastsome synchronization variances so as to update synchronizationinformation. As an example, at least some of synchronization variancesmay be identified according to channel quality of each beam. As anotherexample, at least some of synchronization variances may be identifiedaccording to a tendency of each of the synchronization variances. Thisis because reliability is determined to be low when only one of valuesof the synchronization variances is a negative number and values of theremaining synchronization variances are positive numbers.

FIG. 11 illustrates the specific operations for synchronization trackingaccording to the disclosure. In FIG. 11 , the filtering operation inoperation 1109 is illustrated as being always performed, but thedisclosure is not limited thereto. For example, when a serving beam isscheduled, the terminal may not perform the filtering operation. Duringsynchronization tracking using a serving beam, an effect on the servingbeam incurred by interference may be smaller than those on neighboringbeams.

FIG. 13A illustrates an example of filtering out interference duringany-beam-based synchronization tracking according to various embodimentsof the disclosure. For convenience of description, a beam currentlyscheduled for synchronization tracking by a terminal is referred to as a“pending beam.”

Referring to FIG. 13A, the terminal may receive a synchronizationsignal. The terminal may receive a synchronization signal by using apending beam. The terminal may acquire a first peak 1311 of the pendingbeam during a first synchronization interval. In this example, asynchronization interval is an interval during which a pending beam isscheduled for synchronization tracking, and is referred to as a“periodically-repeated interval during which synchronization of apending beam is tracked.” The terminal may determine, as a first celltime, a time point at which the first peak 1311 is detected during afirst synchronization interval.

The terminal may update an offset so that a time point corresponding tothe first peak 1311 can be a cell time. The terminal may update anoffset so as to determine a second cell time corresponding to the firstcell time during a second synchronization interval which is a nextsynchronization interval. The terminal may determine a synchronizationrange (not illustrated) based on the second cell time. The term“synchronization range” refers to a range for determination of whethersynchronization is successful. In the synchronization range, theterminal may perform correlation calculation so as to detect a peak. Inthe synchronization range, the terminal may detect a synchronizationsignal in the second synchronization interval. A second peak 1312 isexpected to be detected in the synchronization range. Accordingly, theterminal may perform correlation calculation in the synchronizationrange.

The terminal may receive a synchronization signal in the synchronizationrange. The terminal receives a synchronization signal by using thepending beam. The terminal may acquire a third peak 1313 of the pendingbeam during the second synchronization interval. The terminal may detectthe third peak 1313 instead of the second peak 1312. The terminaldetects the third peak 1313 at a position which is away from the secondcell time by a synchronization variance 1315. The terminal may detectthe third peak 1313 so as to determine the synchronization variance1315. For a next synchronization interval, the terminal may apply thesynchronization variance 1315 so as to update synchronizationinformation. In the synchronization range, the terminal may detect notonly the third peak 1313 but also a neighboring peak 1330 of aneighboring cell.

According to various embodiments, the terminal may perform filteringaccording to configuration of a tracking range 1320. The terminal mayconfigure a tracking range with reference to an expected point ofreception of a signal (hereinafter “expected cell time”), that is, asecond cell time. The terminal may cause the tracking range 1320 to benarrower than the synchronization range so as to filter out a peakdetected at a point which is beyond the second cell time. As an example,the terminal may filter out the neighboring peak 1330 of the neighboringcell. The terminal may acquire the third peak 1313 of the pending beam.

FIG. 13B illustrates another example of filtering out interferenceduring any-beam-based synchronization tracking according to variousembodiments of the disclosure. A detailed description of aconfiguration, which overlaps FIG. 13A, will be omitted.

Referring to FIG. 13B, a terminal may receive a synchronization signal.The terminal receives a synchronization signal by using a pending beam.The terminal configures a synchronization range for detection of a firstpeak 1341 of the pending beam during a first synchronization interval.This is because, during a previous synchronization interval, the firstpeak 1341 is expected to be detected at a first cell time. The terminaldetermines the first cell time as an expected cell time in the firstsynchronization interval. The terminal detects a second peak 1342 in thesynchronization range. The terminal determines a time point of detectionof the second peak 1342 as a second cell time.

The terminal updates an offset so that a time point corresponding to thesecond peak 1342 can be a cell time. The terminal may update the offsetso as to determine a third cell time corresponding to the second celltime during a second synchronization interval which is a nextsynchronization interval. The terminal may determine the third cell timeas an expected cell time in the second synchronization interval. Theterminal may determine a synchronization range 1350 based on the thirdcell time. The terminal may detect a synchronization signal in thesecond synchronization interval in the synchronization range 1350. Athird peak 1343 is expected to be detected in the synchronization range1350. Accordingly, the terminal may perform correlation calculation inthe synchronization range 1350.

The terminal may receive a synchronization signal in the synchronizationrange. The terminal receives a synchronization signal by using thepending beam. The terminal may acquire a fourth peak 1344 of the pendingbeam during the second synchronization interval. The terminal may detectthe fourth peak 1344 instead of the third peak 1343. The terminal maydetect the fourth peak 1344 so as to determine a synchronizationvariance 1345. For a next synchronization interval, the terminal mayapply the synchronization variance 1345 so as to update synchronizationinformation. In the synchronization range, the terminal may detect notonly the fourth peak 1344 but also a neighboring peak 1360 of aneighboring cell.

According to various embodiments, the terminal may perform filteringaccording to a gradient of a synchronization variance. If filtering isperformed using only the configuration a tracking range of FIG. 13A,when a peak of a neighboring cell is closer to an expected cell timethan a peak of a serving cell, it is difficult to smoothly filter outthe peak of the neighboring cell. Accordingly, the terminal maydetermine a gradient of a synchronization variance.

A gradient may be a metric representing a tendency of a synchronizationvariance. A synchronization variance is a synchronization error causedby temperature, pressure, and a change with the passage of time, and maybe understood as a phenomenon in which a deviation with the originalreference time point becomes larger as time passes. A cell time offsetmay become larger or smaller as a synchronization interval is repeated.A cell time offset may be changed while maintaining a slope which iseither of a positive number and a negative number. For example, when theterminal has acquired values of synchronization variances which arepositive numbers during previous synchronization intervals but asynchronization variance at a point, at which a peak occurs, is anegative number during a current synchronization interval, the relevantpeak may be determined as a peak of a neighboring cell. The terminal mayfilter out the peak of the neighboring cell. As an example, the terminalmay filter out the neighboring peak 1360 of the neighboring cell. Theterminal may check that the synchronization variance 1345 is a positivenumber, and then may acquire a fourth peak 1344 of the pending beam. Itgoes without saying that filtering according to the disclosure can alsobe similarly applied to a case in which values of synchronizationvariances which are negative numbers have been acquired during previoussynchronization intervals and a neighboring peak has a synchronizationvariance which is a positive number.

FIG. 13C illustrates still another example of filtering out interferenceduring any-beam-based synchronization tracking according to variousembodiments of the disclosure. A detailed description of configurations,which overlap FIGS. 13A and 13B, will be omitted.

Referring to FIG. 13C, a terminal may receive a synchronization signal.The terminal receives a synchronization signal by using a pending beam.The terminal configures a synchronization range for detection of a firstpeak 1371 of the pending beam during a first synchronization interval.The terminal detects a second peak 1372 in the synchronization range.The terminal updates an offset so that a time point corresponding to thesecond peak 1372 can be a cell time. The terminal may update the offsetso as to determine an expected cell time in a second synchronizationinterval which is a next synchronization interval. The terminal maydetermine a synchronization range 1380 based on the expected cell time.A third peak 1373 is expected to be detected in the synchronizationrange 1380. The terminal may acquire a fourth peak 1374 of the pendingbeam during a second synchronization interval. The terminal may detectthe fourth peak 1374 instead of the third peak 1373. The terminal maydetect the fourth peak 1374 so as to determine a synchronizationvariance 1375. In the synchronization range 1380, the terminal maydetect not only the fourth peak 1374 but also a neighboring peak 1390 ofa neighboring cell.

According to various embodiments, the terminal may perform filteringbased on a cell identifier (ID). If only the filtering based on agradient of FIG. 13B is performed, when a peak of a neighboring cell isdetected in the same direction as a direction, in which a peak of aserving cell is detected, with reference to an expected cell time, it isdifficult to smoothly filter out a peak of a neighboring cell.Accordingly, the terminal may compare a cell ID with another so as toperform filtering. The terminal may determine whether a cell ID of asynchronization signal, the peak of which has been detected, coincideswith a cell ID of a serving cell. The terminal may use a sequence of thesynchronization signal, the peak of which has been detected, todetermine whether the cell ID of the synchronization signal correspondsto the cell ID of the serving cell. A synchronization sequence may bepredefined according to the type of synchronization signal. The type ofsynchronization signal may be a PSS, an SSS, or an ESS.

A PSS indicates a cell ID (e.g., 0, 1, 2) within a cell group, and anSSS indicates an ID (e.g., 0, 1, . . . , 167, or 0, 1, . . . , 335) of acell group. According to an embodiment, the terminal may determinewhether a synchronization signal, the peak of which has been detected,has been transmitted from a serving cell, based on whether cell IDswithin a cell group are identical to each other. Also, according to anembodiment, the terminal may determine whether a synchronization signal,the peak of which has been detected, has been transmitted from a servingcell, based on whether cell group IDs are identical to each other.Further, according to an embodiment, the terminal may detect both asynchronization sequence of a PSS and a synchronization sequence of anSSS so as to identify a cell ID. The terminal may determine whether asynchronization signal, the peak of which has been detected, has beentransmitted from a serving cell, based on whether cell IDs are identicalto each other.

An ESS may be scrambled according to a cell ID. According to anembodiment, the terminal may determine whether a synchronization signal,the peak of which has been detected, has been transmitted from a servingcell, based on a cell ID of the serving cell. As an example, theterminal may check a scrambling ID of a sequence of the neighboring peak1390 of the neighboring cell so as to filter out the neighboring peak1390. The terminal: may determine whether a cell ID of a cell, fromwhich a synchronization sequence of the neighboring peak 1390 has beentransmitted, coincides with a cell ID of a serving cell; may determinewhether a cell ID of a cell, from which a synchronization sequence ofthe fourth peak 1374 has been transmitted, coincides with the cell ID ofthe serving cell; and then may filter out the neighboring peak 1390.

On-Demand Interworking

FIG. 14 is a flowchart illustrating an operation of a terminal foron-demand interworking between serving-beam-based synchronizationtracking and beam tracking according to various embodiments of thedisclosure. FIG. 14 illustrates an example of an operating method of theterminal 120. On-demand interworking signifies operations of a terminalfor performing interworking between synchronization tracking and beamtracking only when the need arises and performing beam tracking in othercases.

Referring to FIG. 14 , in operation 1401, the terminal may acquiresynchronization. The terminal may acquire synchronization of a servingbeam. Operation 1401 corresponds to operation 601 of FIG. 6 , and thus adetailed description of the overlapping configuration will be omitted.

In operation 1403, the terminal may determine whether serving-beam-basedsynchronization tracking is needed. Embodiments for determining whetherserving-beam-based synchronization tracking is needed will be describedbelow in detail with reference to FIGS. 15A and 15B. Whenserving-beam-based synchronization tracking is determined to be needed,the terminal may perform operation 1405. When serving-beam-basedsynchronization tracking is determined not to be needed, the terminalmay perform operation 1407.

In operation 1405, the terminal may perform serving-beam-basedsynchronization tracking. The terminal may schedule the serving beam.The terminal may receive a signal by using the serving beam so as toperform synchronization tracking using the serving beam. Operation 1405corresponds to operation 703 of FIG. 7 , and thus a detailed descriptionof the overlapping configuration will be omitted.

In operation 1407, the terminal may perform beam tracking. The terminalmay perform beam tracking of a neighboring beam. The terminal mayreceive a signal by using a neighboring beam so as to measure quality ofthe received signal. The terminal may determine channel quality of theneighboring beam.

When operation 1405 is not performed, in a relevant cycle, the terminalmay not perform synchronization tracking or may perform any-beam-basedsynchronization tracking. For example, when beam tracking of aneighboring beam is performed, the terminal may additionally performsynchronization tracking by using the neighboring beam.

The terminal may perform operation 1407, and then may repeatedly performoperation 1403. According to various embodiments, the terminal maydetermine when to terminate a beam tracking procedure and again performoperation 1403, according to an interworking scheme of the terminal. Forexample, the terminal may determine channel qualities of all theneighboring beams for beam tracking, and may again perform operation1403. Channel qualities of all the neighboring beams are determined, andthus the serving beam may be updated. As another example, the terminalmay again perform operation 1403 whenever a scheduled beam is changed.The terminal may again perform operation 1403 in each measurement unitinterval. As still another example, the terminal may perform beamtracking of neighboring beams, the number of which corresponds to afixed number, and then may again perform operation 1403. As yet anotherexample, the terminal may again perform operation 1403 for each fixedtime.

FIG. 15A is a flowchart illustrating an operation of a terminal fordetermining whether to perform serving-beam-based synchronizationtracking according to various embodiments of the disclosure. FIG. 15Aillustrates an example of an operating method of the terminal 120.

Referring to FIG. 15A, in operation 1501, the terminal may calculate asynchronization variance. A synchronization variance may be asynchronization variance of any beam. Accordingly, a synchronizationvariance may be a synchronization variance of a serving beam or asynchronization variance of a neighboring beam. The terminal maydetermine a synchronization variance based on a difference betweensynchronization information of a pending beam acquired during a previoussynchronization interval and synchronization information of the pendingbeam acquired during a current synchronization interval. Specifically,the terminal may determine a difference between a cell time in aprevious synchronization interval and a cell time in a currentsynchronization interval.

In operation 1503, the terminal may determine whether a synchronizationvariance is larger than a threshold. The terminal may set a threshold toa fixed constant. A threshold may be determined based on trackingperformance of the terminal and peak detection capability of theterminal. The terminal may configure a threshold as a variable.According to an embodiment, a threshold may be determined based on thelength of a CP. The length of a CP is related to a range in which asynchronization error can be allowed. The terminal may configure athreshold so that the threshold becomes larger as the length of a CPbecomes longer. The length of a CP may be determined based on whetherthe CP is a normal CP (NCP) or an extended CP (ECP), or theconfiguration of a subcarrier spacing (SCS). When a synchronizationvariance is larger than the threshold, the terminal may performoperation 1505. When a synchronization variance is not larger than thethreshold, the terminal may perform operation 1507.

In operation 1505, the terminal may determine that serving-beam-basedsynchronization tracking is needed. This is because the possibility ofout-of-synchronization is high when the synchronization variance isexceedingly large (e.g., is larger than or equal to the threshold). Inoperation 1507, the terminal may determine that serving-beam-basedsynchronization tracking is not needed. This is because the possibilityof successful synchronization is high through a compensation procedureusing the synchronization variance in a synchronization range when thedegree of the synchronization variance is slight.

FIG. 15B is a flowchart illustrating another operation of a terminal fordetermining whether to perform serving-beam-based synchronizationtracking according to various embodiments of the disclosure. FIG. 15Billustrates an example of an operating method of the terminal 120.

Referring to FIG. 15B, in operation 1511, the terminal may determinewhether a serving beam has been changed. When channel quality of aneighboring beam is higher than that of a serving beam during beamtracking, the terminal may change the serving beam. In contrast,although channel qualities of all the neighboring beams are determined,when channel quality of a serving beam is higher than those of all theneighboring beams, the terminal may maintain the current serving beamwithout changing the serving beam.

A serving beam signifies a beam having the highest channel quality amongbeams of the terminal, and thus a change of the serving beam may signifya change in a wireless channel between a base station and the terminal.Such a change in a wireless channel may be caused by the movement of theterminal, the entrance of an obstacle into a channel, the passage oftime, or the like. According to a change in a wireless channel, aphysical path for transmission of a signal is changed or a propagationspeed is changed, and thus synchronization may also be changed.Accordingly, the terminal may determine whether to performserving-beam-based synchronization tracking, based on whether to changea serving beam. When the serving beam has been changed, the terminal mayperform operation 1513. When the serving beam has not been changed, theterminal may perform operation 1515.

In operation 1513, the terminal may determine that serving-beam-basedsynchronization tracking is needed. When the serving beam has beenchanged, the terminal may perform synchronization tracking using achanged serving beam. This is because the terminal needs to accuratelyacquire initial synchronization of the changed serving beam.Synchronization acquired at a previous location of the terminal or in aprevious state of a wireless channel is no longer effective at a currentlocation of the terminal or in a current state of a wireless channel. Inoperation 1515, the terminal may determine that serving-beam-basedsynchronization tracking is not needed. This is because the degree ofmovement of the terminal or the degree of a state change of a wirelesschannel is relatively low.

FIG. 15C is a flowchart illustrating still another operation of aterminal for determining whether to perform serving-beam-basedsynchronization tracking according to various embodiments of thedisclosure. FIG. 15C illustrates an example of an operating method ofthe terminal 120.

Referring to FIG. 15C, in operation 1521, the terminal may determinewhether it is possible to perform any-beam-based synchronizationtracking. The terminal may determine whether it is possible to performsynchronization tracking by using other neighboring beams as well as aserving beam. The terminal may determine whether it is possible toperform synchronization tracking by using neighboring beams, based onchannel quality of each of the neighboring beams. For example, whenchannel quality of each of the neighboring beams is lower than or equalto a reference value, the terminal may determine that the neighboringbeams are inappropriate for performing synchronization tracking. As anexample, when the terminal is located on an open path between theterminal and a base station, it may be difficult for the terminal toreceive a signal through a reflected wave by using neighboring beams. Inparticular, when the terminal is located at a cell boundary of the basestation, it may be difficult for the terminal to receive asynchronization signal by using neighboring beams and detect a peak.When it is possible to perform any-beam-based synchronization tracking,the terminal may perform operation 1523. When it is impossible toperform any-beam-based synchronization tracking, the terminal mayperform operation 1525.

In operation 1523, the terminal may determine that serving-beam-basedsynchronization tracking is needed. For beam tracking, the terminalneeds to perform measurement. In order to accurately measure signalstransmitted by the base station, the terminal is required to performsynchronization tracking. However, channel qualities of beams other thana serving beam are inappropriate for synchronization tracking, and thusthe terminal may determine that serving-beam-based synchronizationtracking is needed. In operation 1525, the terminal may determine thatserving-beam-based synchronization tracking is not needed. This isbecause it is possible to perform synchronization tracking by usingneighboring beams.

The conditions for determination of whether serving-beam-basedsynchronization tracking is needed have been described with reference toFIGS. 15A, 15B, and 15C. According to various embodiments, a terminalmay combine at least two of the above-described conditions so as todetermine whether serving-beam-based synchronization tracking is needed.

The embodiments for performing serving-beam-based synchronizationtracking according to the on-demand interworking scheme have beendescribed with reference to FIGS. 14, 15A, 15B, and 15C. However, thedisclosure is not limited thereto. According to various embodiments, aterminal may perform synchronization tracking includingserving-beam-based synchronization tracking and any-beam-basedsynchronization tracking, according to an on-demand interworking scheme.

FIG. 16 is a flowchart illustrating an operation of a terminal forupdating a serving beam according to various embodiments of thedisclosure. FIG. 16 illustrates an example of an operating method of theterminal 120.

Referring to FIG. 16 , in operation 1601, the terminal may perform beamscheduling. The terminal may perform beam sweeping. The terminal maysequentially change a beam according to a defined pattern so as to sweepa beam. The terminal may schedule each of all beams for beam tracking ineach cycle.

In operation 1603, the terminal may perform measurement of a scheduledbeam. The terminal may receive a signal by using the scheduled beam soas to determine channel quality of the received signal. According tovarious embodiments, the terminal may perform synchronization trackingwhile performing measurement. When a signal is received, the terminalmay acquire synchronization information. The terminal may updatesynchronization information by using previous synchronizationinformation of the scheduled beam.

In operation 1605, the terminal may determine whether beam tracking ofall the beams has been performed. In this example, all the beams maysignify beams of the terminal configured for beam tracking. For example,the beams of the terminal configured for beam tracking may be all beamswhich can be supported by the terminal. As another example, the beams ofthe terminal configured for beam tracking may signify all beams whichcan be supported by a particular constituent element (e.g., anRF-antenna) among multiple constituent elements within the terminal.

In operation 1607, the terminal may update the serving beam. Operation1607 corresponds to operation 709 of FIG. 7 , and thus a detaileddescription of the overlapping configuration will be omitted.

FIG. 17 is a block diagram illustrating an example of managingsynchronization information according to various embodiments of thedisclosure. In this example, synchronization information may includeparameters (e.g., a cell time, an offset, and a synchronization range)related to synchronization of a signal received (or transmitted) using abeam. In order to estimate or monitor a synchronization variance byusing any beam, it is necessary to store and manage synchronizationinformation for each beam. Hereinafter, an example of a databaseconfigured to store and manage beam-specific synchronization informationwill be described.

Referring to FIG. 17 , in order to estimate a synchronization varianceof any beam, a terminal may manage synchronization information of eachof all beams for beam tracking. Hereinafter, a situation in which theterminal performs synchronization and beam tracking in a serving cell1710 of a base station will be described by way of example.

When initial synchronization is acquired in an initial access procedure,the terminal may store synchronization information 1727 of an X-th beam1717 which is a serving beam. Thereafter, when a serving beam isscheduled and serving-beam-based synchronization tracking is performed,the terminal may update the synchronization information 1727. Also, evenwhen any-beam-based synchronization tracking is performed, the terminalmay update the synchronization information 1727.

During any-beam-based synchronization tracking, the terminal may usesynchronization information of a neighboring beam. During beam tracking,the terminal may schedule a neighboring beam. Whenever a neighboringbeam is scheduled, the terminal may store synchronization information ofthe neighboring beam. For example, the terminal may sequentiallyschedule a first beam 1711, a second beam 1712, . . . , and an N-th beam1719, and may store synchronization information 1721, 1722, . . . ,1727, . . . , 1729, of a relevant beam. According to the schedulingorder, the terminal may sequentially store and update the first beam1711, the second beam 1712, . . . , and the N-th beam 1719. During beamtracking according to beam sweeping, when the X-th beam 1717 which is aserving beam is scheduled, the terminal may update thepreviously-acquired synchronization information 1727.

The method for scheduling, by a terminal, a beam through interworkingbetween synchronization tracking and beam tracking has been describedabove. When the need arises, the terminal performs synchronizationtracking or controls the number of times of scheduling of neighboringbeams, and thus can improve the performance of synchronization tracking.Also, the terminal schedules neighboring beams by the appropriatefrequency, and thus can optimize the performance of an adaptive link ina beamforming environment. Whether the interworking betweensynchronization tracking and beam tracking according to the disclosureis implemented can be identified according to whether a serving beam isperiodically scheduled. Further, whether the interworking therebetweenaccording to the disclosure is implemented can be identified accordingto whether the terminal detects peaks of synchronization sequences froma neighboring beam as well as a serving beam or whether the terminalstores synchronization information (beam-specific synchronizationinformation).

According to various embodiments, after scheduling of neighboring beams,synchronization information of a serving beam can be updated. Withoutscheduling of the serving beam, a next interval (e.g., at least onesymbol) after scheduling of a neighboring beam, or immediately afterscheduling of a neighboring beam, the terminal can updatesynchronization information (e.g., an offset, an expected cell time, anda synchronization range) of the serving beam. In other words, whetherthe disclosure is implemented can be confirmed through identification ofnon-scheduling of the serving beam between an interval during whichsynchronization information of the serving beam is updated, and aninterval during which a neighboring beam is scheduled.

In the disclosure, in order to determine whether a particular conditionis fulfilled, the expression “greater than or equal to (or greaterthan),” or the expression “less than or equal to (or less than)” isused, but this expression is only a description for expressing anexample, and thus does not exclude the description “greater than (orgreater than or equal to),” or the description “less than (or less thanor equal to)” For example, a condition described by the expression“greater than or equal to” can be replaced by a condition described bythe expression “greater than.” A condition described by the expression“less than or equal to” can be replaced by a condition described by theexpression “less than.” A condition described by the expression “greaterthan” can be replaced by a condition described by the expression“greater than or equal to.” A condition described by the expression“less than” can be replaced by a condition described by the expression“less than or equal to.” A condition described by the expressions“greater than or equal to” and “less than” can be replaced by acondition described by the expressions “greater than” and “less than orequal to.” A condition described by the expressions “greater than” and“less than or equal to” can be replaced by a condition described by theexpressions “greater than or equal to” and “less than.”

Methods according to claims of the disclosure or embodiments describedin the specification thereof may be implemented in hardware, software,or as a combination of hardware and software.

When the methods are implemented in software, a computer-readablestorage medium configured to store one or more programs (softwaremodules) may be provided. The one or more programs stored in thecomputer-readable storage medium may be configured to be executable byone or more processors within an electronic device. The one or moreprograms may include instructions that cause the electronic device toperform the methods according to claims of the disclosure or embodimentsdescribed in the specification thereof.

The programs (software modules or software) may be stored innon-volatile memories including a random access memory (RAM) and a flashmemory, a read only memory (ROM), an electrically erasable programmableROM (EEPROM), a magnetic disc storage device, a compact disc-ROM(CD-ROM), a digital versatile disc (DVD), other type optical storagedevices, or a magnetic cassette. Alternatively, the programs may bestored in a memory implemented by a combination of some or all of theabove-described memories. Further, the electronic device may include aplurality of such memories.

Also, the programs may be stored in an attachable storage device whichmay access the electronic device through a communication network, suchas the Internet, the Intranet, a local area network (LAN), a wide LAN(WLAN), or a storage area network (SAN), or through a communicationnetwork implemented by a combination thereof. Such a storage device mayaccess a terminal configured to perform embodiments via an externalport. Further, a separate storage device on the communication networkmay access a terminal configured to perform embodiments.

In the above-described specific embodiments, an element included in thedisclosure is expressed in a singular or plural form according to apresented specific embodiment. However, the singular or pluralexpression is appropriately selected according to the presentedsituation for convenience of description, and the disclosure is notlimited to a single element or multiple elements thereof. An elementexpressed in the plural form may be configured as a single element, oran element expressed in the singular form may be configured as multipleelements.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A terminal in a wireless communication system,the terminal comprising: at least one transceiver; and a controllercoupled with the at least one transceiver, and configured to: determinea first beam as a serving beam of the terminal based on channelqualities of a plurality of beams of the terminal, obtainsynchronization information of the first beam of the terminal, obtain afirst difference between a previous cell time of a second beam of theterminal and a current cell time of the second beam, wherein the secondbeam is different from the first beam, obtain new synchronizationinformation of the serving beam according to the first difference,obtain at least one channel quality of the plurality of beams based onthe new synchronization information, and update the serving beam basedon the obtained at least one channel quality.
 2. The terminal of claim1, wherein the controller is, in order to obtain the new synchronizationinformation, further configured to: obtain a second difference between aprevious cell time of the first beam of the terminal and a current celltime of the first beam of the terminal and obtain the newsynchronization information of the serving beam according to the seconddifference.
 3. The terminal of claim 2, wherein the controller isfurther configured to: before receiving a signal using the serving beam,obtain channel qualities of first neighboring beams different from theserving beam in a first beamforming interval, and after receiving thesignal using the serving beam, obtain channel qualities of secondneighboring beams different from the first neighboring beams in a secondbeamforming interval.
 4. The terminal of claim 3, wherein a number ofthe first neighboring beams and a number of the second neighboring beamsare constants.
 5. The terminal of claim 3, wherein a number of thesecond neighboring beams scheduled in the second beamforming interval isdetermined based on at least one of a synchronization variance of theserving beam or the channel qualities of the first neighboring beams. 6.The terminal of claim 2, wherein the controller is further configuredto: based on identifying that one of the first difference or the seconddifference is larger than or equal to a designated threshold, obtain asynchronization tracking by scheduling the serving beam.
 7. The terminalof claim 2, wherein the controller is, in order to obtain the seconddifference, further configured to: obtain the previous cell time byreceiving a signal using the first beam in a first cycle, and obtain thecurrent cell time by receiving at least one signal by using the firstbeam in a second cycle subsequent to the first cycle.
 8. The terminal ofclaim 1, wherein the controller is further configured to: in case that,among the at least one channel quality of the plurality of beams, achannel quality higher than a channel quality of the first beam exists,change the serving beam to a beam corresponding to a highest channelquality among the plurality of beams, and in case that, among the atleast one channel quality of the plurality of beams, the channel qualityhigher than the channel quality of the first beam does not exist,maintain the first beam as the serving beam.
 9. The terminal of claim 1,wherein the synchronization information of the serving beam comprises acell time offset of a serving cell.
 10. The terminal of the claim 9,wherein the new synchronization information is obtained by compensatingthe cell time offset of the serving cell using the first difference. 11.A method performed by a terminal in a wireless communication system, themethod comprising: determining a first beam as a serving beam of theterminal based on channel qualities of a plurality of beams of theterminal; obtaining synchronization information of the first beam of theterminal; obtaining a first difference between a previous cell time of asecond beam of the terminal and a current cell time of the second beam,wherein the second beam is different from the first beam; obtaining newsynchronization information of the serving beam according to the firstdifference; obtaining at least one channel quality of the plurality ofbeams based on the new synchronization information; and updating theserving beam based on the obtained at least one channel quality.
 12. Themethod of claim 11, wherein the updating obtaining of the newsynchronization information comprises: obtaining a second differencebetween a previous cell time of the first beam of the terminal and acurrent cell time of the first beam of the terminal, and obtaining thenew synchronization information of the serving beam according to thesecond difference.
 13. The method of claim 12, before receiving a signalusing the serving beam, obtaining channel qualities of first neighboringbeams different from the serving beam in a first beamforming interval,and after receiving the signal using the serving beam, obtaining channelqualities of second neighboring beams different from the firstneighboring beams in a second beamforming interval.
 14. The method ofclaim 13, wherein a number of the first neighboring beams and a numberof the second neighboring beams are constants.
 15. The method of claim13, wherein a number of the second neighboring beams scheduled in thesecond beamforming interval is determined based on a synchronizationvariance of the serving beam.
 16. The method of claim 12, furthercomprising: based on identifying that one of the first difference or thesecond difference is larger than or equal to a designated threshold,obtaining a synchronization tracking by scheduling the serving beam. 17.The method of claim 12, wherein the obtaining of the second differencecomprises: obtaining the previous cell time by receiving a signal usingthe first beam in a first cycle; and obtaining the current cell time byreceiving at least one signal by using the first beam in a second cyclesubsequent to the first cycle.
 18. The method of claim 11, furthercomprising: in case that, among the at least one channel quality of theplurality of beams, a channel quality higher than a channel quality ofthe first beam exists, changing the serving beam to a beam correspondingto a highest channel quality among the plurality of beams, and in casethat, among the at least one channel quality of the plurality of beams,the channel quality higher than the channel quality of the first beamdoes not exist, maintaining the first beam as the serving beam.
 19. Themethod of claim 11, wherein the synchronization information of theserving beam comprises a cell time offset of a serving cell.
 20. Themethod of the claim 19, wherein the new synchronization information isobtained by compensating the cell time offset of the serving cell usingthe first difference.